winpr/tools: fix building shared libs

libwinpr-makecert-tool.a is used to build libxfreerdp-server.so, so even
if we are building a static libwinpr-makecert-tool.a library, we need to
build it with -fPIC.

Patch and commit log suggested by Samuel MARTIN.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Samuel Martin <s.martin49@gmail.com>

diff -durN freerdp-440916eae2e07463912d5fe507677e67096eb083.orig/winpr/tools/makecert/CMakeLists.txt freerdp-440916eae2e07463912d5fe507677e67096eb083/winpr/tools/makecert/CMakeLists.txt
--- freerdp-440916eae2e07463912d5fe507677e67096eb083.orig/winpr/tools/makecert/CMakeLists.txt	2014-08-25 06:52:43.000000000 -0700
+++ freerdp-440916eae2e07463912d5fe507677e67096eb083/winpr/tools/makecert/CMakeLists.txt	2014-10-24 15:39:39.600319523 -0700
@@ -43,3 +43,8 @@
 
 set_property(TARGET ${MODULE_NAME} PROPERTY FOLDER "WinPR/Tools")
 
+if(BUILD_SHARED_LIBS)
+	# build libwinpr-makecert-tool.a with PIC because it is used to build
+	# the shared library libxfreerdp-server.so.
+	set_property(TARGET ${MODULE_NAME} PROPERTY POSITION_INDEPENDENT_CODE TRUE)
+endif()
